Hydraulic motors and pumps having vane elements in both the rotor and stator are old as shown in Pat. No. 3,672,797. However, for a successful and long-life operation, such fluid power converters depend upon a proper interaction or crossing of the stator and rotor vanes. It has been found that the shape and size of the rotor and stator vane tips or crossing edges are an important influence on successful vane crossings. Because it is a practical impossibility to produce a commercial fluid power converter with zero radial clearance between the rotor and stator adjacent the vane slots, some convex curvature of the rotor and stator vanes is required to prevent the sides of the vanes from locking one on the other in the clearance space between the rotor and stator. While circular vanes, such as shown in Pat. No. 2,992,616 prevent the stator and rotor vanes from locking their excessive curvature creates undesirable detenting action, particularly under conditions of either high speeds or heavy loads as well as causing high friction losses. Additionally, it has been found that it is undesirable to have any coacting contours between the rotor and stator with the vanes which includes any sharp surfaces which undesirably produces rapid wearing of the vanes and their coacting surfaces on the rotor and stator.
Therefore, the present invention provides for improvements in the shape and size of rotor and stator vane tips or crossing edges which prevent vane locking, detenting, and minimizes wear.